Medical balloons are used in the body in a variety of applications including as dilatation devices for compressing plaque and for expanding prosthetic devices such as stents at a desired location in a bodily vessel. Because it is typically necessary for the balloon to traverse a tortuous anatomy as it is being delivered to the location in a bodily vessel, it is desirable for the balloon to assume as low a profile as possible.
One way to achieve a low profile is by folding the balloon to form a number of wings. Current technologies typically employ a number of hard dies, which are moved radially inward toward the center of a partially inflated balloon. The balloon is maintained in a partially inflated state until the dies have reached the end of their stroke. A vacuum is then applied to the balloon to deflate the balloon and form wings that conform to the configuration of the dies. The wings may then be wrapped or rolled around the circumference of the balloon. This method is not effective, however, for forming wings with undercuts or multiple layers.
Where a balloon with wrapped wings is used to expand a stent, a rotational moment is imparted on the stent as a result of the unfolding of the wings as the balloon expands. The interaction between the stent and the balloon may cause undesirable wear to the stent and/or balloon. Where the stent comprises a coating, the rotational movement may damage the coating and may damage the wall of the vessel in which the stent is located.
Balloons with rolled wings also exhibit non-circular, irregular cross-sections. The irregular cross-section can facilitate contact between adjacent struts of a crimped-on stent. This contact can, in turn, lead to bonding between adjacent struts on coated stents when the stent is sterilized and the coating softens.
There remains a need for innovative methods for folding balloons, which avoid some of the problems that may result, in certain circumstances, from balloons having rolled wings. There also remains a need for innovative methods for folding balloons, in particular where multi-layer folds are desired.
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Without limiting the scope of the invention a brief summary of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
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